The invention relates to agents for the surface treatment of flat insulating materials having a base of aromatic polyamides.
Flat insulating materials serve as insulating materials in highly stressed electric machines, for example, as cover slides for stator and armature slots. Such flat insulating materials must exhibit good electrical, thermal and mechanical properties, and therefore, they generally consist of aromatic polyamides or a combination of aromatic polyamides with other insulating materials, for example, with a polyester base. Of great significance are, for example, aromatic polyamides of m- or p-phenylene diamine and terephthalic acid.
In utilizing aromatic polyamides as flat insulating materials, the poor bond between the polyamide surface and the impregnating resins applied thereon is disadvantageous. Cover slides for stator and armature slots, for example, must accordingly have small manufacturing tolerances so that sufficient strength can be obtained. In the assembly, where the outside of the cover slides glides the walls of the slot insulation and at the same time, the winding inserted into the slot pushes the cover slide hard upward, the force required is very large due to the large friction forces that occur. In addition, this large force often leads to trouble in the production cycle due to jamming and breakage and to increased manufacturing costs.
The reason for the poor workability is that the flat insulating materials used, for example, the cover slides of aromatic polyamide, have a rough surface structure, which is particularly the case with fabrics and with paper pressed from fibers. It has been attempted, therefore, to avoid the above-mentioned difficulties through the use of lubricants. For this purpose, the surfaces of the flat insulating materials are treated with silicone or paraffin oil. Although this makes possible the insertion of the cover slides into the stator or armature slots without excessive effort, the adhesion between the flat insulating material and the subsequently applied impregnating resin is further reduced by this measure. Indeed, silicone oils cause a complete separation between the impregnating resin and the surface of the flat insulating material.